Controller for internal combustion engine

ABSTRACT

A controller for controlling the combustion timing of an internal combustion engine and a method for controlling the ignition timing of an internal combustion engine in which variations in combustion timing as detected from the pressure in the combustion chamber of the engine and the intensity of knocking are simultaneously detected and the ignition timing corrected to provide optimum combustion efficiency at all times. From the sensed pressure in the combustion chamber, the crank angle at which the maximum pressure occurs is determined. If the crank angle thus determined exceeds a first reference value, a first ignition time correcting signal is generated. If the knocking intensity exceeds a second reference value, a second ignition timing correcting signal is generated. The output signal utilized to correct the ignition timing is produced by selecting one of the two ignition timing correcting signals thus generated, wherein the second ignition timing correcting signal has priority over the first ignition timing correcting signal.

BACKGROUND OF THE INVENTION

The present invention relates to a controller for an internal combustionengine. More particularly, the invention relates to a method of anapparatus for adjusting the ignition timing of an engine in such amanner as to suppress knocking without excessive delays of ignition,thereby to provide a high engine efficiency at all times.

In recent years, there has been a trend in the field of internalcombustion engines towards the use of lean mixture combustion to providereduced fuel consumption and cleaner exhaust emissions. Also, it hasbecome more common to use superchargers to achieve higher combustionefficiency. With these techniques, remarkable improvements have beenachieved.

These newly developed techniques have, however, been accompanied byproblems such as fluctuations of the fuel flow rate due to increasedfluctuation of the crank angle at which the maximum pressure of thecombustion gas is established. Also, knocking problems have become moresevere. As is well known, the generation of knocking increases vibratorypressures with the frequency of the vibratory pressure being related tothe pressure in the combustion chamber. Hitherto, in order to minimizeknocking, feedback control of ignition timing has been implementedutilizing sensing of the vibratory pressure with a vibration sensorattached to the engine body with the ignition timing being adjusted inaccordance with the output of the sensor. This conventional controlsystem, however, is unsatisfactory from the viewpoint of reducing fuelconsumption in engines designed to operate with a lean air-to-fuel ratiomixture.

SUMMARY OF THE INVENTION

In order to overcome these drawbacks, the present invention provides amethod and apparatus for controlling combustion in an internalcombustion engine in which both variations in combustion timing andknocking are detected simultaneously, and signals indicative of theseparameters are employed to optimize combustion efficiency.

More specifically, according to one aspect of the invention, there isprovided a method of controlling combustion in an internal combustionengine including the steps of sensing, using a pressure sensor, thecrank angle corresponding to the time of generation of maximum pressurein the combustion chamber, and, if the sensing output signal is delayedbeyond a predetermined reference value, advancing the angle of ignitiontiming corresponding to the frequency of occurrence of such delaysand/or the amount of delay; and sensing, by means of a knock sensor, theknocking intensity and, if the knock sensing output signal is higherthan a predetermined reference level, effecting an adjustment of theadvance angle of the ignition timing corresponding to the frequency ofsuch an output and/or the amount by which the reference level isexceeded.

According to another aspect of the invention, there is provided acontroller for a internal combustion engine including a pressure sensorfor sensing changes in the gas pressure within the combustion chamber ofthe engine; a circuit for detecting the moment of maximum pressure fromthe output of the pressure sensor; a maximum-pressure crank angledetecting circuit receiving as one input thereto the maximum-pressuremoment signal; a first comparator circuit for comparing the output fromthe maximum-pressure crank angle detecting circuit with a referencevalue to produce a signal for correcting the ignition timing in responseto the result of the comparison; a circuit for detecting the knockingintensity from the output of the pressure sensor; a second comparatorfor comparing the knocking intensity signal with a reference value andfor producing a delay correction signal for correcting the ignitiontiming in response to the result of the comparison; and a selectioncircuit for selectively delivering the output from the first comparatorcircuit or the output from the second comparator circuit thereby toeffect feedback control of combustion through adjustment of ignitiontiming.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pressure sensor attached to a cylinder head for use in aninternal engine controller of the invention;

FIG. 2 is a block diagram of an internal engine controller of apreferred embodiment of the invention;

FIG. 3 shows the details of a selection circuit used in the controllerof FIG. 2;

FIGS. 4A and 4B are timing charts showing waveforms of various signalsin the circuits shown in FIGS. 2 and 3 at locations designated bycorresponding symbols; and

FIG. 5 is a logic diagram of a detecting circuit (reference numeral 4)used in the controller of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be described in detail with reference topreferred embodiments.

Referring first to FIG. 1, reference numeral 101 denotes a pressuresensor of a type having two superposed structures, each of whichincludes a lead titanate-zirconate piezoelectric element covered on bothsides with metal layers to form a laminated structure. Electrode platesare interposed between the two structures. The pressure sensor 101 ismounted in the fashion of a washer with a head bolt 104 on a cylinderhead 103 on the cylinder block 102. In multi-cylinder engines, pluralsuch pressure sensors 101 are provided for plural selected cylinderswith each sensor mounted with a head bolt on which is imposed theinternal pressure of the corresponding cylinder. The pressure sensors inthat case are electrically connected in parallel with one another toprovide a single output.

Referring now to FIG. 2, which is a block diagram of a control apparatusof the invention, a high input impedance amplifier 1 boosts the outputfrom the sensor 101 to produce a waveform indicated as a signal a inFIG. 4A. The signal a is smoothed by a lowpass filter 2 to provide asignal b in FIG. 4A. Reference numeral 3 denotes a circuit, implementedwith a differentiating circuit, which is used to detect the moment atwhich the pressure waveform reaches its maximum value. Reference numeral4 denotes a circuit which detects the crank angle corresponding to themoment of maximum pressure.

A first projection is provided on one side, for instance, of a discwhich is directly connected to the crank shaft at a position suitablefor indicating the top-dead-center (TDC) crank position, and a firstangle sensor (reference sensor) is disposed adjacent the path ofrotation of this projection. It is also possible to use pluralprojections, two or three, for instance, for this purpose. A set ofsecond projections is formed on the periphery of the disc at positionsremoved from the first set of projections at angular intervals of 1°,for instance. A second angle sensor is disposed in the vicinity of thepath of rotation of the latter projections.

With reference to FIG. 5, the circuit 4 for detecting the crank anglecorresponding to the moment of maximum pressure includes an RS flip-flop21 which receives the output (signal c in FIG. 4A) from the circuit 3indicating the moment of maximum pressure on its R (Reset) input and theoutput (signal d in FIG. 4A) from the first (reference) crank angleposition sensor on its S (Set) input. The circuit 4 further includes anAND gate 22 which receives the output Q from the flip-flop 22 and the 1°angle signal from the second sensor. An integrator circuit composed of acounter 23 and D/A converter 24 is provided for integrating the outputof the AND gate 22. The counter 23 is reset to the all zeroes state bythe signal c. With this arrangement, the height of the output (signal ein FIG. 4A) from the integrator circuit represents the crank angle atthe moment of maximum cylinder pressure.

An angle comparator/detector circuit 5 compares the signal e with apreset reference (limit) value V_(H) and produces, when the referencevalue is exceeded, a signal in the form of pulses constituting anignition timing correction signal (advance angle correction signal inthis case), shown as signal f in FIG. 4A. Reference numeral 6 denotes aknock frequency bandpass filter (high-pass filter). The output from thepressure sensor (signal a in FIG. 4A) is modified into the signal g inFIG. 4A as it passes through the filter 6. A wave-shaping circuit 7rectifies and smoothes the signal g thereby to produce an output (signalh in FIG. 4A) representing the intensity of knocking. A knock intensitycomparator/detector circuit 8 compares the knock intensity signal h witha reference (limit) value V_(H) ' and produces, when the reference valueis exceeded, a delay angle correction signal (signal i in FIG. 4A) forthe ignition timing in the form of a pulse signal.

A selection circuit 9 is provided to select one of the two correctionsignals (signal f and i). The selection circuit, as shown in FIG. 3 ofthe preferred embodiment, gives priority to the ignition timing delayangle correction signal i for suppressing knocking. When this signal isin the active state, a monostable multivibrator 91 is triggered toproduce an output which is applied to the gate of an AND gate circuit 92which gates the ignition timing correction signal f, thereby to cut-offthe combustion delay correction signal f by producing an output signalf', as seen in FIG. 4B. The selection circuit 9 may be of a type whichis switchable according to a specific operating parameter of the enginebetween a first mode in which terminals 10 and 11 are connected to eachother while terminals 12 and 13 are disconnected from each other and asecond mode in which terminals 10 and 11 are disconnected from eachother while terminals 12 and 13 are connected to each other.

Reference numeral 16 denotes an ignition timing setting (computing)device of known construction which computes and determine the optimumignition timing from signals from outputs of an engine speed sensor, aload sensor (boost pressure sensor) and a coolant temperature sensorand, in response thereto, applies an ignition signal to an ignitioncoil. The ignition timing setting device 16 is capable of correcting theignition timing in accordance with signals applied through signal inputterminals 14 and 15. In FIG. 4B, waveform k illustrates the manner ofcorrection of the ignition timing in accordance with the above-describedcorrection signal.

As has been described above, according to the invention, both the delayof combustion and the generation of knocks are sensed and the correctionof the ignition timing is effected selectively in accordance with thesensed parameter. As a consequence, according to the invention, thecombustion efficiency of the engine is significantly improved whileexhaust emissions are advantageously simultaneously reduced.

I claim:
 1. A method for controlling the combustion in an internalcombustion engine, comprising the steps of: sensing a crank angle ofsaid engine corresponding to a time of maximum pressure in a combustionchamber of said engine; sensing a reference crank angle; providing afirst ignition timing correcting signal when the sensed crank angle isdelayed beyond said reference crank angle; sensing a knocking intensity;producing a second signal for correcting said ignition timing when saidsensed knocking intensity exceeds a predetermined reference level; andeffecting correction of said ignition timing in response to one of saidfirst and second ignition timing correcting signal with said secondignition timing correcting signal having priority over said firstignition timing correcting signal, and wherein said step of correctingsaid ignition timing in accordance with one of said first and secondignition timing correcting signals comprises inhibiting said firstignition timing correcting signal for a predetermined time period inresponse to said second ignition timing correcting signal.
 2. Acontroller for controlling the combustion in an internal combustionengine comprising: a pressure sensor for sensing a gas pressure within acombustion chamber of said engine; means for detecting a moment ofmaximum pressure from an output of said pressure sensor; a crank anglesensor; a maximum-pressure crank angle detecting circuit for determiningin response to outputs from said pressure detecting means and said crankangle sensing means a crank angle at which a maximum pressure in saidcombustion chamber occurs; first comparing means for comparing an outputof said maximum-pressure crank angle detecting circuit with a firstpredetermined reference value for producing a first ignition timingcorrecting signal when the crank angle at which said maximum pressureoccurs exceeds said first predetermined reference value; knockingintensity detecting means operating in response to an output of saidpressure detector; second comparing means for comparing a knockingintensity signal produced by said knocking intensity detecting meanswith a second predetermined reference value for producing a secondignition timing correcting signal when the detected knocking intensityexceeds said second predetermined reference value; and selecting circuitmeans for delivering as an output ignition timing correcting signal oneof said first and second ignition timing correcting signals, whereinsaid second ignition timing correcting signal has priority over saidfirst ignition timing correcting signal, and wherein said selectingmeans comprises means for inhibiting from said output ignitioncorrecting signal said first ignition timing correcting signal for apredetermined time after said second ignition timing correcting signalis received.
 3. A controller for controlling the combustion in aninternal combustion engine comprising: a pressure sensor for sensing agas pressure within a combustion chamber of said engine; means fordetecting a moment of maximum pressure from an output of said pressuresensor; a crank angle sensor; a maximum-pressure crank angle detectingcircuit for determining in response to outputs from said pressuredetecting means and said crank angle sensing means a crank angle atwhich a maximum pressure in said combustion chamber occurs; firstcomparing means for comparing an output of said maximum-pressure crankangle detecing circuit with a first predetermined reference value forproducing a first ignition timing correcting signal when the crank angleat which said maximum pressure occurs exceeds said first predeterminedreference value; knocking intensity detecting means operating inresponse to an output of said pressure detector; second comparing meansfor comparing a knocking intensity signal produced by said knockingintensity detecting means with a second predetermined reference valuefor producing a second ignition timing correcting signal when thedetected knocking intensity exceeds said second predetermined referencevalue; and selecting circuit means for delivering as an output ignitiontiming correcting signal one of said first and second ignition timingcorrecting signals, wherein said second ignition timing correctingsignal has priority over said first ignition timing correcting signal,and wherein said crank angle sensor comprises a disc coupled to berotated by the crank of said engine, said disc having a first projectionat a position indicative of a top-dead-center crank angle, and aplurality of second projections spaced at equal intervals on said disc;and first and second stationarily mounted projection sensors for sensingsaid first projection and said projections, respectively, for producinga top-dead-center position signal and an incremental angle signal,respectively, said first comparing means comprising an RS flip-flop, anAND gate, a counter, and an analog-to-digital converter, said flip-flophaving an R input coupled to receive said maximum-pressure signaloutputted by said pressure detecting means, an S input coupled toreceive said top-dead-center position signal, and a Q output coupled toa first input of said AND gate, said AND gate having a second inputcoupled to receive said incremental angle signal and an output coupledto a clock input of said counter, said counter having a reset inputcoupled to said R input of said flip-flop and outputs coupled to digitalinputs of said digital-to-analog converter, an output of saiddigital-to-analog converter forming said first ignition timingcorrecting signal.